Ureteral wall thickness at the stone site: A critical predictor of success and complications in children undergoing semi-rigid ureteroscopy

Abstract

We retrospectively assessed the role of ureteral wall thickness (UWT) at the ureteral stone site in predicting the stone-free status and the complication rates in children undergoing semi-rigid ureterorenoscopy (URS). The children who underwent URS and had undergone non-contrast abdominal computerized tomography before the URS were included in the study. The following protocol was used to determine the outcome. Immediately before removing the stent, all children were evaluated by ultrasound (US) and plain film (KUB) for residual stones in the upper urinary tract and after removing the double J stent, the presence of stone fragments in the ureter was checked with URS. The children were considered stone-free if no residual fragments were identified in radiologic imaging and the evaluation of the ureter by URS. The case was accepted as a failure if any fragments were seen on immediate US, KUB, and/or during URS just after the stent removal. The patients who could not complete the standard primary URS procedure due to stone-related reasons (patients for whom we could not pass the safety guidewire behind the stone and/or the procedure was terminated due to pyuria during the procedure) were also accepted as a failure. The possible factors related to the patient, stone, ureter, and the operation that could affect the outcome and the complications following the URS were evaluated. The children's median age was six years (1-17 years). Among the 89 children included in the study, 69 (78%) were stone-free, and 20 (22%) presented residual stone after the first URS session. The ROC analysis revealed that a UWT value of 4.5mm (sensitivity 60%, specificity 92%) was the optimal cut-off value predictive of the URS outcome. The regression analysis revealed UWT >4.5mm (p=0.006) and multiple stone presentation (p=0.005) as independent risk factors for residual stone. Complications were detected in 15 (17%) children. Thick ureteral wall (p=0.012) and longer operative time (p=0.016) were defined as the independent risk factors for complications. Increased UWT is associated with the adverse outcomes of URS due to tissue hypertrophy, edema, and mucosal bleeding may cause difficulty in removing the stone. The thick ureteral wall might increase the risk of complications due to the necessity of manipulating the instruments or the involuntary forceful use of instruments while removing the stone. UWT was the only independent variable affecting both increased failure and complication rates in children undergoing URS.